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E Gleichmann

Publications and source records attributed to E Gleichmann.

At least 37 records · Page 2Linked to original sources
PubMed1996

Alteration of a model antigen by Au(III) leads to T cell sensitization to cryptic peptides.

Certain metal ions are known to be potent sensitizers, but the self proteins modified by metal ions and the self peptides recognized by 'metal-specific' T cells are unknown. In humans and mice treatment with gold anti-rheumatic drugs, containing Au(I), may lead to allergic and autoimmune side effects. Human and murine T cells do not react to Au(I), however, but to the reactive metabolite Au(III). Here we show that alteration by Au(III) of a model antigen, bovine ribonuclease (RNase)A, results in T cell sensitization to cryptic peptides of this protein. Upon immunization of mice with Au(III)-pretreated RNase [RNase/Au(III)], CD4+ T cell hybridomas specific for RNase/Au(III) were obtained in addition to those recognizing the immunodominant peptide RNase 74-88; the latter also were obtained after immunization with native RNase. RNase/Au(III)-specific T cell hybridomas reacted against RNase/Au(III) and RNase denatured by S-sulfonation of cysteine residues, but not against native RNase, or RNase pretreated with Au(I), A1(III), Cu(II), Fe(II), Fe(III), Ni(II), Mn(II), or Zn(II). Using a panel of overlapping, synthetic RNase peptides which were devoid of gold or gold-induced modifications, epitope mapping revealed that RNase/Au(III)-specific T cell hybridomas recognized the cryptic peptides 7-21 and 94-108, respectively. Comparison of the proliferative response of bulk CD4+ T cells, prepared from splenocytes after immunization with either RNase/Au(III) or native RNase, revealed that Au(III) pretreatment of RNase led to a markedly enhanced response to the two cryptic peptides while it did not influence the response to the immunodominant peptide. The cryptic peptides were also presented after preincubation of bone marrow-derived macrophages with RNase and Au(I), but not with RNase alone, suggesting that oxidation of Au(I) to Au(III) and subsequent protein alteration by Au(III) can happen in mononuclear phagocytes. We conclude that Au(III) alteration of proteins alters antigen processing and, thus leads to presentation of cryptic peptides. This mechanism may shed light on the development of allergic and autoimmune side effects of Au(I) anti-rheumatic drugs. In addition, it might provide a general mechanism of how metal ions act as T cell sensitizers.

Amino Acid Sequence↗
PubMed1996

Silicotic lymph node reactions in mice: genetic differences, correlation with macrophage markers, and independence from T lymphocytes.

Quartz was injected into a hind food of BALB/c and DBA/2 mice and on days 40, 90, and 180 the progressive response ensuing in the draining popliteal lymph node (PLN) was investigated by histopathology and immunohistopathology. The area of silicotic nodules (ASN) was measured by morphometry, and, by this parameter, strain BALB/c proved to be a high responder to quartz, and strain DBA/2 a low responder, albeit both strains showed a similar degree of reactive lymphoid hyperplasia in the draining PLN. Both strains also showed a similar quartz content in the draining PLN but in BALB/c mice quartz particles were concentrated in the ASN, whereas in DBA/2 mice they were evenly dispersed over the PLN. Because the silicotic response of athymic BALB/c nu/nu mice was even stronger than that of euthymic BALB/c mice, T cells are not required for the development of silicotic nodules. This fits the notion that quartz is not an antigen and that high and low responder strains are MHC-identical. Because quartz-treated BALB/c, but not DBA/2 mice, showed a persistent expression of the macrophage differentiation markers MRP8 and MRP14, phenotypically the observed strain difference in silicotic responsiveness seems to be expressed at the level of macrophages.

Animals↗
PubMed1996

T cells ignore the parent drug propylthiouracil but are sensitized to a reactive metabolite generated in vivo.

The antithyroid drug propylthiouracil (PTU) is known to cause adverse immunological side effects, such as a lupus-like syndrome and vasculitic disorders. In vitro experiments have established that myeloperoxidase of activated neutrophils can oxidize PTU to the reactive intermediate propyluracil 2-sulfonate PTU-SO3-, and it has been proposed that PTU-SO3- might be responsible for the PTU-associated side effects. Here, using the direct popliteal lymph node assay (PLNA) in mice we found that PTU-SO3-, indeed, induced a T-cell-dependent primary PLN response, whereas the parent compound PTU failed to do so. As shown by adoptive transfer PLNA, splenic T cells of mice that had received four injections of PTU-SO3- mounted a specific secondary response to the reactive metabolite, but not to PTU. When homogenized peritoneal phagocytes, which had been incubated with PTU in vitro, were used as the antigen, a primary response in the direct PLNA was elicited, suggesting that the phagocytes contained the reactive metabolite. Moreover, T cells sensitized to the reactive metabolite PTU-SO3- were detected in mice that were undergoing long-term treatment with PTU plus an additional treatment with phorbol myristate acetate for stimulation of the oxidative metabolism of their phagocytic cells. Together, these findings support the concept that phagocytes oxidize PTU to its immunogenic metabolite, PTU-SO3-, which then, presumably via covalently binding to self-proteins, induces T cell sensitization.

Animals↗
PubMed1996

Murine systemic autoimmune disease induced by mercuric chloride: T helper cells reacting to self proteins.

HgCl2 induces a CD4+ T-cell-dependent systemic autoimmune disease in susceptible strains of rats and mice. In rats, autoreactive T cells were shown to be involved, whereas in mice, attention has focussed on the demonstration of 'Hg-specific' T cells. To clarify these seemingly different T cell involvements, T cells from B10.S mice treated with HgCl2 for 1 or 8 weeks were analyzed for their capacity to mount anamnestic responses against various self antigens (Ags) which either contained Hg or did not. T cells from donors short-term treated with HgCl2 failed to mount memory responses to Hg-free Ags, but mounted a significant response to HgCl2 and also reacted with Hg-containing self Ags. Interestingly, T cells from donors long-term treated with HgCl2 showed a different pattern of reactivity. They hardly reacted to HgCl2 and reacted poorly to Hg-containing splenic proteins, but responded vigorously to nuclei and fibrillarin irrespective of whether these self constituents had been treated with HgCl2 or not. Conceivably, the initial activation of T cells that recognize Hg in combination with nuclear self proteins, such as fibrillarin, eventually results in activation of T cells specific for the unaltered self proteins.

Animals↗
PubMed1996

Persistence of decreased T-helper cell function in industrial workers 20 years after exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

In experimentally exposed animals 2,3,7,8-tetrachlorodibenzo-n-dioxin (TCDD) causes severe immunosuppression. However, the overall susceptibility of humans for the different pathological effects of TCDD has remained unclear. We examined the long-term effects of TCDD in 11 industrial workers who were exposed to high doses of TCDD for several years 20 years ago. Current TCDD body burdens were still at least 10 times higher (between 43 and 874 pg/g blood far) in these exposed persons than in the average German population. To evaluate possible TCDD-induced changes in the percentage of different lymphocyte subsets, we determined a large panel of lymphocyte subsets in the blood by flow cytometric analysis. Immunocompetence of T-and B-lymphocytes was tested by nitrogen (phytohemagglutinin, pokeweed mitogen)- induced lymphoproliferation assays and by assays using sensitive mixed-lymphocyte cultures. No significant differences could be detected between the individuals tested and controls for surface marker distribution or mitogen-induced lymphoproliferation TCDD-exposed subjects showed a reduced response to human lymphocyte antigen-allogeneic lymphocytes and interleukin-2-boosted proliferation. Responder cells of the dioxin-exposed persons proliferated less in response to irradiated stimulator cells (p < or = 0.05), and the third-party mixed lymphocyte reaction against unirradiated stimulator cells revealed suppressive activity in the responder cell fraction compared to the controls (p < or = 0.01). Furthermore, the capacity of a pool of T cells isolated from TCDD-exposed subjects to proliferate upon interleukin-2 stimulation was significantly diminished (p < or = 0.05). TCDD has a long-term immunosuppressive-effect on T-helper cell function, which is mediated more likely by a reduced functionality of individual cells rather than by a reduction in absolute cell numbers in the peripheral blood.

Animals↗
PubMed1996

The popliteal lymph node assay in mice: screening of drugs and other chemicals for immunotoxic hazard.

The popliteal lymph node assay (PLNA) in mice represents a predictive test for assessing the sensitizing (allergenic and autoimmunogenic) potential of drugs and low molecular weight chemicals. Measuring activation of the draining lymph node of the hind paw, the PLNA facilitates the detection and analysis of immunotoxic effects in a rapid and reproducible manner. An attractive feature of the PLNA is that it can be performed in combination with the routine toxicity testing required for new drugs. Thus, it is possible to investigate whether animals exposed by the oral, intravenous, or inhalative route have been sensitized to the test compound or a reactive metabolite of the test compound generated in vivo. PLNAs may be appropriate supplements to routine toxicity screening of chemicals, thereby enhancing chemical safety.

Administration, Inhalation↗
PubMed1995

The antirheumatic drug disodium aurothiomalate inhibits CD4+ T cell recognition of peptides containing two or more cysteine residues.

The mechanism of action of antirheumatic gold drugs, such as disodium aurothiomalate (Au(I)TM), has not been clearly identified. Gold drugs inhibit T cell activation induced by mitogen and anti-CD3 mAb in vitro at relatively high concentrations. However, since gold drugs fail to induce immunosuppression in vivo, the pharmacologic relevance of this finding is doubtful. In this study, we asked whether Au(I)TM interferes with processing and presentation of defined Ags to T cells. Using a panel of murine CD4+ T cell hybridomas, we found that low concentrations of Au(I)TM (< or = 10 microM) led to a markedly reduced IL-2 release of T cell hybridoma clones that recognized peptides containing two or more cysteine (Cys) residues, such as bovine insulin A1-14. Since disodium thiomalate alone had no effect, the inhibition was due to Au(I). IL-2 production induced by anti-CD3 mAb stimulation was not affected by the low concentration of Au(I)TM used. Au(I)TM had no effect on the presentation of peptides containing no or only one Cys residue(s). In contrast to the unmodified insulin peptide A1-14, Au(I) could not inhibit recognition of an insulin peptide in which Cys residues in positions 6 and 11 were replaced by serine. Most likely, the observed inhibition is mediated by formation of chelate complexes between Au(I) and two Cys thiol groups of the affected antigenic peptides. The peptide-specific inhibitory effect of Au(I) on Ag presentation described here might contribute to the therapeutic effect of Au(I) compounds in rheumatoid arthritis.

Amino Acid Sequence↗
PubMed1995

CD8 thymocytes derived from 3,3',4,4'-tetrachlorobiphenyl-exposed fetal thymi possess killing activity.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and its congeners such as 3,3',4,4'-tetrachlorobiphenyl (TCB) cause immunosuppression in experimental animals and possibly in humans. In previous studies we found that exposure of murine fetal thymic organ cultures (FTOCs) to TCDD or TCB reduced the proliferative capacity of immature thymocytes. At the same time, the kinetics of thymocyte maturation was changed, and thymocyte differentiation was skewed toward CD4-CD8+ phenotypically mature cells. Here, we analyze the biological activities of thymocytes generated in TCB-exposed fetal thymus to determine whether these cells are also functionally mature. C57BL/6 fetal thymic lobes from Day 15 of gestation were explanted and grown for 8 days in FTOC in the presence or absence of 3.3 microM TCB. Then, the functions of total thymocytes or sorted subsets thereof were tested. We found that thymocytes from TCB-exposed lobes responded to stimulation by Con A or anti-CD3 and possessed cytotoxic activity upon cultivation in the presence of H-2 allogenic spleen cells. Further analysis showed that the overall cytotoxic activity of thymocytes was mainly due to the CD4-CD8+ cells. Our results suggest that the CD4-CD8+ cells, which are generated in substantially increased numbers in TCB-exposed fetal thymus, are functionally competent cells.

Animals↗
PubMed1995

Phagocytes render chemicals immunogenic: oxidation of gold(I) to the T cell-sensitizing gold(III) metabolite generated by mononuclear phagocytes.

The oxidizing capacity of phagocytic cells is suspected to play a major role in the generation of immunogenic drug metabolites, in particular those that cause extrahepatic immunopathological lesions. In the case of the antirheumatic drug gold(I) disodium thiomalate (Na2Au(I)TM), oxidation of the Au(I) ion to Au(III) appears to be responsible for the adverse immune reactions which may develop during gold therapy. Here, we show that the reactive metabolite Au(III) may be generated by mononuclear phagocytes (M phi) exposed to Au(I). The generation of Au(III) was analyzed by means of the adoptive transfer popliteal lymph node assay (PLNA) in mice, using T lymphocytes previously sensitized to Au(III) as a detection probe. Donors of the Au(III)-primed T cells were either directly sensitized to Au(III) by injection of tetrachloroauric acid (HAu(III)Cl4), or indirectly via chronic treatment with Na2Au(I)TM. As donors of peritoneal cells (PC), we used mice which had received weekly i.m. injections of Na2Au(I)TM for 12 weeks and contained increased numbers of activated B cells. The PC of these mice were found to elicit a significant secondary response when used as antigenic material for the restimulation of Au(III)-primed T cells. The immunogenicity of PC obtained from Na2Au(I)TM-treated mice paralleled the total gold content of these cells. Noteworthily, M phi exposed to Au(I) in vitro also proved capable of eliciting a specific secondary response of Au(III)-primed T cells. Hence, M phi exposed to Au(I) generate the reactive intermediate Au(III) which, apparently via oxidation of self proteins, sensitizes T cells. As M phi are constituents of many different organs and, moreover, communicate with T cells, their capacity to generate Au(III) may account for the various extrahepatic adverse immune reactions induced by Au(I) drugs.

Animals↗
PubMed1995

Metal ion induced autoimmunity.

Metal-induced autoimmunity is a well established but poorly understood phenomenon. Recent work has begun to elucidate the molecular interactions of metal ions with immune cells and self-proteins. Metal-induced presentation of cryptic self-peptides emerges as a possible mechanism for activation of 'metal-specific' T cells, challenging the hypothesis of a random polyclonal activation of T and B cells by metals. A preferential T-helper cell type 2 response is involved in metal ion induced systemic autoimmune disease.

Animals↗
PubMed1995

Mercuric-chloride-induced autoimmunity in mice involves up-regulated presentation by spleen cells of altered and unaltered nucleolar self antigen.

HgCl2 treatment of B10.S mice induces IgG autoantibodies to fibrillarin, a component of small nuclear ribonucleoprotein particles, and histone. Here, we demonstrate the activation by HgCl2 of autoreactive T cells specific for these nuclear proteins. Of nine CD4+ T cell hybridoma clones obtained from HgCl2-treated B10.S mice, one clone reacted to histone Hl and eight clones to fibrillarin. One of the fibrillarin-specific clones only recognized fibrillarin pretreated with HgCl2 (Hg2+ fibrillarin), suggesting that Hg2+ can induce the presentation of a novel fibrillarin epitope. Four fibrillarin-specific hybridoma clones studied for cytokine production were shown to produce interleukin (IL)-2, and three of them also produced IL-4. For stimulation of fibrillarin-specific T cell hybridomas, exogenous murine fibrillarin had to be added when antigen-presenting cells (APCs) came from untreated mice, but not when the APCs were obtained from HgCl2-treated animals. Apparently, HgCl2 treatment induces the presentation by APCs of a novel Hg2+ fibrillarin epitope and up-regulates the presentation of unaltered fibrillarin epitopes, thus activating 'Hg(2+)-specific' as well as autoreactive CD4+ T cells.

Animals↗
PubMed1995

Predictive immunotoxicological test systems: suitability of the popliteal lymph node assay in mice and rats.

This article reviews results obtained with popliteal lymph node assays (PLNAs) in rodents and discusses their ability to detect and analyze immunotoxic effects of drugs and other low molecular weight (LMW) chemicals. In its basic form, the PLNA measures activation of the draining lymph node of the hind paw (i.e., the PLN) after injection of a test chemical into the hind foot pad. The assay appears to be appropriate to recognize sensitizing, that is, allergenic and autoimmunogenic, chemicals, as well as nonsensitizing immunostimulatory chemicals. With modifications, PLNAs can detect immunosuppressive chemicals and distinguish sensitizing from nonsensitizing chemicals. Furthermore, modified PLNAs enable detection of known as well as unknown sensitizing metabolites, and may assist in the identification of the self-molecules that act as carriers for chemical sensitization or as targets of chemical-induced autoimmune disease. Experience with PLNAs shows that they are rapid, reproducible, and objective tests for recognition of sensitizing or otherwise immunomodulating chemicals. Because current protocols of toxicity testing are insensitive in predicting a chemical's potential to result in immunomodulation, PLNAs, when further validated, may provide welcome supplements to routine toxicity screening of chemicals, thus enhancing chemical safety.

Animals↗
PubMed1994

Thymic stroma exposed to arylhydrocarbon receptor-binding xenobiotics fails to support proliferation of early thymocytes but induces differentiation.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and 3,3',4,4'-tetrachlorobiphenyl (TCB), two ubiquitous environmental pollutants, accelerate thymocyte maturation, and eventually lead to thymus atrophy. These processes are mediated by binding of TCDD or TCB to the cytosolic arylhydrocarbon receptor (AhR) abundant in the thymus, which acts as a ligand-activated transcription factor. At several stages of their maturation thymocytes need the interaction with thymus stroma. We tested whether thymocytes themselves or the thymus stroma are targets of AhR-binding compounds for interference with thymocyte maturation. We depleted fetal thymus lobes from proliferating cells, i.e., thymocytes, by treatment with deoxyguanosine and recultivated them with immature thymocytes (CD4-CD8-), exposing either the stroma or the thymocytes to TCDD or TCB before recultivation. Although CD4-CD8- immature thymocytes could differentiate in TCB-treated stroma, expansion of the cells was severely impaired. Selective exposure of thymocytes to AhR-binding compounds likewise did not impair the capacity of differentiation of CD4-CD8- thymocytes. These cells, however, could expand when transferred into new lobes that had not been exposed to TCDD or TCB. TCB treatment of fetal thymi leads to an accumulation of phenotypically mature CD4-CD8+ cells. We show here that these cells do not belong to the transient CD4-CD8+ thymocytes, as previously suggested, because in recultivation experiments they do not give rise to any thymocyte subset further down the maturation pathway.

Animals↗
PubMed1994

The specificity of disease-associated anti-fibrillarin autoantibodies compared with that of HgCl2-induced autoantibodies.

Autoantibodies against nucleolar components are a common serological feature of patients suffering from scleroderma, a collagen vascular autoimmune disease. An important target of these autoantibodies is a protein with an apparent molecular weight of 36 kDa and a pI value of 8.5, located in the dense fibrillar component of the nucleolus and therefore termed fibrillarin. Animal models in which abundant anti-nucleolar antibodies appear spontaneously have not yet been described; however, high levels of anti-fibrillarin antibodies can be induced by treating susceptible strains of mice with sub-toxic amounts of mercuric chloride. In this study, we have analysed the specificity of anti-fibrillarin autoantibodies of human and murine origin. Our results suggest that both species have similar, if not identical conformational epitopes that are the target of anti-fibrillarin autoantibodies; these epitopes require the presence of a 30-kDa fragment of the fibrillarin molecule. Post-translational modifications such as the dimethylation of arginines in the N terminus of the protein are not essential for antibody recognition.

Animals↗
PubMed1994

Gold kinetics under long-term treatment with gold(I) disodium thiomalate: a comparison in three different mouse strains.

Following weekly i.m. injections of gold(I) disodium thiomalate (GST), mice of strains A.SW and C57BL/6 develop adverse immune reactions, whereas DBA/2 mice do not. We have studied the pharmaco-toxicokinetics of gold in these strains under chronic GST treatment. Our results indicate that the susceptible strains A.SW and C57BL/6 accumulate significantly higher gold concentrations in the liver and spleen compared to the resistant strain DBA/2. In the kidney of DBA/2 mice, gold concentrations persisted at a plateau level, whereas in A.SW and, particularly, C57BL/6 mice early peaks of gold concentrations were followed by a transient decrease, suggestive of tubular toxicity. Whereas splenic T and B cells failed to contain measurable gold concentrations in all three strains, splenic and peritoneal macrophages contained relatively high levels, more so in the susceptible strain C57BL/6 than in the resistant DBA/2 strain. This finding is consistent with the concept that macrophages play an important role in both the adverse and the beneficial effects of gold drugs.

Animals↗
PubMed1994

3,3',4,4'-Tetrachlorobiphenyl inhibits proliferation of immature thymocytes in fetal thymus organ culture.

The environmental pollutant 3,3',4,4'-tetrachlorobiphenyl (TCB) leads to thymic atrophy and immunosuppression, the former possibly causing the latter. TCB binds to the cytosolic aryl-hydrocarbon receptor (AhR) and transforms it into a DNA-binding state. The development of fetal thymocytes is severely affected by TCB and other AhR-binding xenobiotics, leading to a skewed pattern of thymocyte maturation stages. Murine thymocyte proliferation after exposure to TCB was studied in fetal thymus organ culture (FTOC). C57BL/6 fetus thymic lobes from day 15 of gestation were explanted and grown for 2, 4, 6, and 8 days in organ culture in the presence or absence of 3.3 microM TCB. Subsets of thymocytes were defined by CD4 and CD8 surface markers, and their cell cycle was analysed by DNA staining with 7-amino-actinomycin D (7-AAD). Exposure of fetal thymi in vitro to 3.3 microM TCB significantly reduced the total number of thymocytes, and fewer thymocytes were in S/G2M phase. The inhibition of cell proliferation induced by TCB treatment affected mainly the CD4-CD8- (double-negative, DN) and CD4-CD8+ (single-positive, SP) subsets, and these inhibition appeared mainly in more immature thymocytes, i.e. DNCD3- and CD8+CD3- subpopulations, whereas no effect of TCB on CD4+CD8+ (double-positive, DP) cell proliferative activity was observed. Analysis of the relation of cell proliferation and development of subsets in differentiating fetal thymocytes suggests that TCB enhanced thymocyte differentiation into mature CD8+ cells.

Animals↗